1. Field of the Invention
The invention relates to an occupant restraint system for a motor vehicle.
2. Description of the Prior Art
Modern occupant restraint systems, such as for example belt pretensioners or driver or passenger airbags, are intended to be triggered only in the event of, for example, a frontal or angled collision. On the other hand, triggering should not take place in the event of bumpy roads, electromagnetic incompatibility or as the result of a fault within the electronic circuit. On account of the latest generation of so-called smart airbags and the ever more frequent use of electronic front sensors on the vehicle, increasingly shorter triggering times are also being obtained for passive restraining means.
Malfunctions of the occupant restraint system are currently prevented by a mechanical acceleration sensor, known as the safing sensor. Mechanical safing sensors (for example ball in tube, Rollamite, etc.) are based on a different physical principle than electronic acceleration sensors. In this case, electrical disturbances can influence the electronic sensors much more severely than is the case with mechanical sensors. For example, the triggering of an airbag only takes place when the electronic sensor initiates triggering and, moreover, the mechanical sensor (mechanical switch function) is closed. However, instances of erroneous airbag triggering caused by unfavorable road conditions cannot be prevented in every case by means of a mechanical sensor, since the vibrations may cause the mechanical sensors to be closed.
The use of electronic acceleration sensors, in particular in the crash zone of the vehicle (for example front or early crash sensors) allow ever shorter triggering times for occupant restraint systems. On the other hand, even today the available mechanical sensors sometimes no longer achieve the closing time required for this. A further increase in the sensitivity of the overall occupant restraint system by lowering the response threshold of the mechanical sensors does not appear to be advisable on account of the associated increasing frequency of closing under normal driving conditions.